Production of electrodes



W. K. PAGE. PRODUCTION or Euzcmones.

APPLICATION HLED MN. l0. l9l6.

Patenfed May 6, 1919.

O ED009000 OOQOGOO OQOOOGO O O OD GO GOO,

OQOGOO 'OOOGOO OGOOO OOOOG ATTORNEYS UNIT D s'ratrns PATENT OFFICE.

WILLIAM 'KINGMAN PAGE, or cnrcneo, ILLINOIS, ASSIGNOR TO CHILI nxrnomnon COMPANY, or New YORK, N. 1., A CORPORATION on NEW JERSEY.

rnonuc'rroiw or ntncmonns.

To'allwhom it may concern:

Be it known that I. VILLIAM IiINCMAN- a full, clear, and exact description of the invention, such as will enable others skilled in the art to which it appertains to make and use the same.

The present invention relates to the production of an electrode particularly adapted for use in electrolytic operations where it is desirable to have electrodes of ample conductivit to subserve their intended urpose and which will nevertheless be insouble in the electrolyte in which they are employed.

Electrodes made in accordance With the present invention are of particular use in the electrolytic production of caustic soda and in the electrolysis of the leach liquors of ores, as, for instance, the solutions obtained by the leaching of copper orother ores with sulfuric or hydrochloric acid. In the accompanying drawing,are shown suitable embodiments of the invention. In said drawing- 1 Figure '1 represents, in side elevation, a metal plate (shown broken away intermediate of its length, for convenience of illustration) suitable for use as a core ormain bod portion of the electrode;

Fig. 2 represents a like view of the said core with its protecting sheath-o1 insoluble material firmly anchored thereto, the. whole. constituting a completed insoluble electrode;

Figs. 3 and 4: represent, respectively, crosssectional views of Figs. 1 and 2.

Fig. 5 represents a cross-sectional View of a, modified form of core plate, and

Fig. 6 represents a solid cast electrode with a core plate embedded therein.

Similar letters of reference indicate similar parts in both views. I v

In carrying'out' the invention, the core or main body portion of the electrode consists of ametal plate of ample conductivity with which is intimately associated a fused. outer coating of material insoluble in the electrolyte for which the electrode is intended. Thus, the core a of the electrode shown in the drawing-may consist ofsoft iron or mild steel, or of silicon iron or "steel or ferro- Specification of Letters Patent.

silicon, and it is important that the material chosen I shall have the same, or approximately the same, coefficient of expansion as the coating material 6 fused thereto, so that, Within the range oftemperatures to which the electrode issubjected in practical use there will be no tendency for the fused coating to develop fissures or cracks into which the electrolyte could penetrate to attack the metal beneath. p The coating 1) will consist preferably of magnetite containing usually from 5to 7% of silica most or all of which is derived from the usual silica content of, the magnetite.

The magnetite is fused in any suitable electric furnace, or the like, and, it is preferred to add to it a few per cent. (say 2 to 3%) of alumina for the purpose of toughening it and thereby decreasing any tendency to crack after 1t has been applied to the core.

To apply the fused material to the core, it is preferred to dip the core in a molten bath of the said material, and to quickly withdraw it from the molten bath so as. to permit the dip coating to chill and shrink into close surface union With the metal of the core. To facilitate the adhesion of :the fused material to the metal, it is referred to first pickle the core, in the usua manner employed, for instance, in the tin-plating industry, for the purpose of de-oxidizing and removing the surface scale. To the clean metallic surface left after the pickling Patented May 6, 1919. Application filed January 10, 1916. Serial No. 71,211.

the coating, of fused magnetite. 'llhe molten material, during the dipping operation, enters and occupies the series of apertures, and upon the quick withdrawal of the plate, the molten material setsin said apertures, partly or wholly filling them, and, in any even-t,locking the coating as a Whole to the core. The coreis thus incased in a, thin, tough and anchored coating of material, insoluble inthe electrolyte for Which-the electrode is intended and of a co-eilicient of expansion so closely identical with that of the metal of the core that, within the range of temperatures met with in the use of the electrode, there will be no tendency to the development of cracks or fissures suflicient to permit the electrolyte to reach the metal core.

It will be preferable and desirable to iv-e the electrode a second coating of the mo ten material, after it has received its first coating. This second coating may likewise be applied bydipping. It serves, moreover, not only to reinforce the first coating, with which it blends into a homogeneous union, but also covers any parts which may have been left uncoated in the first dipping. Furthermore, the application of the magnetite in two coatings has the additional advantage, of very considerable practical importance, that the first coating may be applied by quickly immersing the core plate and as quickly withdrawing it, so that it may not be in the molten bath for any longer period of time than is necessary for its immersion and immediate withdrawal. Consequently, the tendency for the molten magnetite to burn the iron core plate is correspondingly minimized. In the second dipping operation, any imperfections of the first are cured, and the initial coating serves as a protector to the metal core sheet within. As indicated at the upper part of Fig. 2, it will be convenient to leaveuncoated the upper part of the metal core sheet, so that the electrode may be coupled up appropriately in the circuit by the customary connections, not shown.

In order to further toughen the coating, it will be desirable, in some cases, to anneal it for several days in a body of inert pulverulent material, such as kieselguhr (infusorial earth), powdered pumice, powdered quartz, or the like.

. Under the conditions of practice of the invention as described, the magnetite may be regarded as fused to the surface of the iron or steel core by a bond which is probably magnetic iron oxid formed on the iron surface itself during the dippingoperation. This probability is indicated by the extreme tenacity of union between the iron surface and the magnetite coating, it being impossible to separate the coating from the iron by any clean plane of cleavage. In the completed electrode, nevertheless, the iron core retains its desired conductivity, throughout its entire extent, appropriate to its use as an insoluble anode in the electrolytic art, and the relatively thin coating of magnetite ofi'ers no excessive resistance for the uses intended,

while it is nevertheless adapted to withstand, without injury, the rough handling usually encountered in industrial operations.

The electrode above described, and illus- I trated by Figs. 1 to 4, can be used directly as an electrode, or it can be used in the production of cast electrodes having a much larger body of the magnetite cast therewith. In the production of cast electrodes, the coating or coatings of the magnetite protects the core plate in much the same manner that the first layer of magnetite protects pings into the molten magnetite.

A cast electrode having a larger body of magnetite cast therewith, is illustrated in cross section in Fig, 6. In the production of this cast electrode, the mold is previously heated to a temperature of about 350 C. and may with advantage have a removable hot top or pouring funnel thereon forming an extension in which the molten magnetite can be poured. In producing the cast elec; trode, the molten magnetite'is poured into the mold through. the funnel or hot top until both the mold and the removable top are.

completely filled, and the .mold is then allowed to stand undisturbed for a period which may vary, in practice, for example, from ten to sixty seconds, depending upon the size of the mold. This is for the purpose .of allowing a shell of magnetite to form in contact with the walls of the mold. Before removing the hot top or pourlng funnel, the

-the core plate during the subsequent dipiron or steel core may be immersed into the as kieselguhr, to prevent its being cooled too rapidly. If the coated cores have been otherwise produced, their production in this mannerwlll not be necessary, but in the rapid production of cast'electrodes the coated cores may with advantage be produced in this manner.

Afterthe core or screen has been thus coated, or after the shell of magnetite has been first produced, within the mold, where the coated core has 'been' otherwise roduced, the removable pouri I ;funnel or ot top is knocked off with a efe'aring efi'ect, thereby leaving the mold filled with the magnetite, the outer portion of which is solid and of uniform thickness, and the inner portion of which is still molten. A coated screen or core, which has been coated by a previous operation, is quickly thrust down into the a when inserted in the mold. Thus, with a mold 4% inches wide, the core might be about 3 inches wide. The length of the core might, with adruantage, be somewhat greaterthan the depth of the mold, for instance, 4 inches greater over all, in the case center the coated core, while the coating upon the core protects it from the corrosive action of the-molten magnetite. Before this 'coatingupon the core can be penetrated, the temperature of the mass will be so lowered that the whole will be solidified. This is important, both in order to protect the screen or, core, and to insure an intimate contact between it and the body of magnetite surrounding it. .With an uncoated screen, there is danger of reaction and of destruction if it is immersed and allowed to remain in the molten magnetite without previous coating, and the union between the coreand the magnetite body may be ofan imperfect nature. It is accordingly of advantage to use a coated core, or a core which is otherwise of'a nature so that it will not be injuriously acted upon by the' body of molten magnetite.

As soon as the body of the electrode is solidified, it is quickly removed from the mold, and transported by appropriate means, suitably supported throughout its length, to a soaking or annealing furnace, such as a mufiie furnace previously heated to .an 'approprate temperature, where it is allowed to remain fora period varying from, for instance, 5 to 15 minutes. This treatment serves to adjust the strains set up by any difi'erence in expansion of the magnetite and its core, and thus prevent cracking during cooling. After this treatment the electrodes are removed and placed in a body or bed of inert pulverulent material such as kieselguhr, etc.

Where the core is of material which does not lend itself readily to punching or perforating, such as ferro-silicon or silicon steel, the core'can be cast with ribs, arranged longitudinally thereof, and these ribs may also, with advantage, be undercut, as indicated in the cross section of Fig. 5- in order to make the union between the core and the body or coating of magnetite more secure. The use of cores of ferro-silicon or of silicon iron or steel presents the, ad-

vantage that by suitably regulating thecontent of sllicon the co-efiicient of expansion can be made substantially the same as that g of the magnetite so that danger of splitting OH or cracking of the coating or body of magnetite will be thereby minimized. I Ferro-silicon or silicon steel is furthermore of an acid resisting nature, and when used as a core,

. is but little attacked by the electrolyte even I when exposed. When thus exposed, the resuits obtained seem t0 indicatethat the current tends to pass from the core through the magnetite to the electrolyte rather than comprising a core sheet of meta directly from the core to the electrolyte,

thereby further reducing the corrosion of the core.

It may be stated generally, that it has been found appropriate and convenient to make the coresof about t of an inch in thickness and from 3 to 4.- feet in height,

and of a width of, for example, 3 to 5. inches, so that the completed electrode, with its coating or body of magnetite, may be readily handled, and so that it may be of moderate weight where it is employed in the electrolysis of copper ore solutions in operations conducted on a large scale. It will be understood, however, that the dimensions of the electrode may vary with the particular purpose for which theelectrodes are to be employed, and that the illustrations given are but typical of its many possible em-' bodiments in practice.

What I claim is: 1. An electrode for electrolytic purposes,

comprising a core sheet of metal, and an 1 3. An electrode for electrolytic purposes,

comprising a core sheet of soft iron or mild steel, provided with a series of apertures in close proximity to each other, and a body or coating fused thereto consisting mainly of magnetite; substantially as described,

4. An electrode for electrolytic purposes, comprising acore sheet of soft iron or mild steel, provided with a series of apertures in close proximity to each other, and a body or coating fused thereto consisting mainly of magnetite together with silica; substantially as described.

5. An electrode for electrolytic purposes, comprising a core sheet of soft iron or mild steel, provided with a series of apertures in close proximity to each other, and a body orcoating fused thereto consisting mainly of magnetite together with silica and alu, mina; substantially asdescribed.

' 6. An electrode for electrolytic purposes,

comprising a core sheet of soft iron or mild steel, and a flowed dip coating fused there- 'to consisting mainly of magnetite, said coating having substantially the same heat coefiicient o to consisting mainly of magnetite, said coating having substantially the same heat co- 1purposes,

expansion as that of the core sheet; substantially as described.

comprising a core sheet of metal having a flowed di coating fused thereto consisting mainly 0 magnetite and a body consisting mainly of magnetite cast around said coating, said coating and cast bod having substantially the same heat coe cient of expansion as that of the core sheet; substantially as described.

9. The method of producing electrodes for electrolytic purposes, which comprises im- 'mersmg a core sheet of metal in a molten body of a coating conductive material insoluble in the proposed electrolyte and withdrawing said sheet before injury thereto, whereby an outer coating of the material is fused to said sheet; substantially as described.

10. The method of producing electrodes for electrolytic purposes, which comprises immersing a core sheet of metal in a molten body consisting mainly of magnetite and withdrawing said sheet before injury thereto, whereby an outer coating of the magnetite is fused to said sheet; substantially as described.

11. The method of producing electrodes for electrolytic purposes, which comprises immersing a core sheet of metal in a molten body consisting mainly of magnetite and withdrawing said sheet before injury thereto, whereby an outer coating of the magnetite is fused tosaid sheet, and repeating the immersion to form a further coating upon the coated sheet; substantially as described.

12. The method of producing electrodes for electrolytic purposes, which comprises immersing a core sheet of metal in a molten body consisting mainly of magnetite and withdrawing said sheet before injury there to, whereby an outer coating of the magnetite is fused to said sheet, and casting a -body of magnetite around the coated sheet by inserting such sheet in a body of the magnetite and allowin the body to solidify; substantially as descri ed.

13. The'method of producin electrodes for electrolytic purposes, whic comprises pouring molten magnetite into a heated mold and allowing the same to stand until a sheet of magnetite is formed in contact with the walls of the mold, then inserting a metal sheet coated with magnetite into the still molten interior of the mold and allow-- ing the molten magnetite to solidify, whereby the shell of ma netite first formed serves to guide the meta sheet, and whereby the coating of magnetite upon such sheet pro tects it from the action of the molten magnetite; substantially as described.

14. The method of producing electrodes magnetite, removing the solidified. electrode from the mold and holding the same at the high temperature to anneal the same, and then slowly cooling the electrode; substantially as described.

' In testimony whereof I aflix m signature.

- WILLIAM KINGMA PAGE. 

